220 ELEMENTS OF BOTANY. 



118. RUBIACEiE. MADDER FAMILY. 



Herbs, shrubs or trees ; leaves simple, opposite or whorled ; 

 flowers perfect, regular, axillary or terminal ; calyx tube 

 adherent to the ovary, the limb 4-6-toothed or wanting ; 

 corolla rotate to funnel-form, 4-6-lobed, inserted in the throat 

 of the calyx ; stamens inserted in the throat of the corolla, 

 as many as its lobes and alternate with them ; ovary 1-sev- 

 eral-celled, style single ; fruit a capsule, drupe or berry. 



I. HOUSTONIA. 



Annual, biennial or perennial herbs ; stems erect or diffuse ; 

 leaves entire, stipules often only a line connecting the bases 

 of opposite leaves ; flowers small, solitary or clustered ; calyx 

 4-toothed, persistent ; corolla rotate to funnel-form, 4-lobed ; 

 stamens 4 ; ovary 2-celled, style slender, stigmas 2 ; fruit 

 a 2-celled, few-many-seeded capsule, dehiscent at the apex, 

 which is free from the calyx. 



1. H. ccERULEA L. Bluets. Perennial, from very slender 

 rootstocks ; stems tufted, erect, smooth, forking, 3-6 in. high ; leaves 

 sessile, often ciliate, the lower spatulate, the upper lanceolate ; flowers 

 solitary, on slender, axillary peduncles ; calyx small ; corolla salver- 

 form, blue or white, yellow in the throat ; flowei'S of two forms, 

 the stamens exserted and the style short in one form, while in the 

 other the stamens are short and the style exserted ; capsule laterally 

 compressed, 2-lobed, shorter than the calyx. February- April. Com- 

 mon on open ground. 



2. H. MINOR (Michx.) Britt. Small Bluets. Annual; stem 

 erect, branched at the base, forking above, smooth, 2-4 in. high; 

 lower leaves oval to ovate, petioled, the upper narrower and sessile ; 

 flowers solitary, on slender, axillary peduncles, blue or white ; calyx 

 small ; lobes of the corolla about as long as the tube ; stamens and 

 style exserted or included ; capsule compressed, as long as the calyx. 

 February- April. Common on dry, open ground. 



3. H. PURPUREA L. Large Bluets. Perennial; stem stout, 

 erect, simple or branched, smooth or pubescent, 4-angled, 6-12 in. 

 high ; leaves ovate to ovate-lanceolate, sessile or short-petioled, 3-5- 

 nerved, often ciliate on the margins; flowers in terminal cymes, 

 purple to nearly white ; corolla funnel-form, the tube longer than 



